Method of dissolving difficultly soluble metal sulfates



Patented July 4, 1950 METHOD or mssewme'nmwtmy SOLUBLEMETAL SULFATES" Albert H. Angerman, Oak RidgeQTen'ng :assignor t the United States of America as represented: by theUnited States Atomic Energy.-Commission N0 Drawing. Application Octob erlY, 19 44, 'SerialNo.559,132 1 i 7 Claims. (01. 2s-s12 1 This invention relates to a method for dissolving diflicultly soluble materials. More particularly this invention concerns a method of ,dissolving certain diflicultly soluble sulfate compounds by utilizing a zirconium nitrate type of.

by means of strong acids, as for example by the use of fuming sulfuric acid, it is apparent that use of such strong acids may be hazardous and involve other problems such as corrosion.

I have found that by the use of 'a simple solvent comprising a zirconium nitrate solvent as described herein, difilcultly soluble compounds of the type aforementioned may be dissolved.

This invention has for one object to provide a method of dissolving difficultly soluble compounds.

Still another object is to provide a method of dissolution that is particularly applicable to the dissolution of difficultly soluble sulfates.

A still further object is to provide a method of dissolving difficultly soluble derivatives of lead, calcium, strontium and barium.

Still another object is to provide a new meth- 0d of dissolution involving the use of a zirconium nitrate type of solvent.

A still further object is to provide a method of producing solutions of difficultly soluble sulfates which solutions are relatively stable toward dilution.

Other objects will appear hereinafter.

I have found that difficultly soluble compounds of the type referred to may be dissolved in a zirconium nitrate type of solvent even at room temperatures. However, the dissolution is usually facilitated by Warming; consequently temperatures up to 100 C. are preferably employed.

The zirconium nitrate type of solvent used is not required to be of any fixed concentration, but the solvent may comprise from a few grams of the zirconium. nitrate compound dissolved in water or other suitable liquid, to a saturated solution thereof. The choice of any particular concentration of zirconium type solvent and the amount thereof to use would depend upon the compound to be dissolved, its particular condition and related factors. Certain of the diificultly soluble sulfates referred to herein are very soluble in the zirconium nitrate solvent ofthe present invention; hence, relatively small amounts of the dilute solventmay be used.

A further understanding of my invention may be had from a consideration of the following examples wherein dissolution procedure. has been carried out. In these examples the solvent employed was of a'concentration comprising approx-- imately 187 grams of zirconium, as the oxyn'itrate, also referred to a zi'rconyl nitrate, dissolved in each literof' distilled water. That is, the weight indicated refers only to the zirconium, the weight of, the particular radicalassociated therewith 'beingdisregarded in: making up the solvent. :The zirconium was ina+4valence state. i Samples comprising 1 gram each 'of'the following sulfates were treated,in'amely, sulfates of calcium, lead, strontium, and barium.:.The. solvent and the sulfate were thoroughly mixed togethen with warming; The 'first'two sulfates, namely calcium and lead sulfates, were very soluble in the zirconium nitrate solvent and went into solution relatively quickly.

The strontium sulfate did not dissolve as quickly and was regarded, as respects the other sulfates, as only moderately soluble. The barium sulfate under the described conditions of concentration of zirconium nitrate solvent, the quantity thereof and temperature of dissolution dissolved the least quickly of all of the difficultly soluble compounds. However, by increasing the quantity of solvent to about 200 (30., complete dissolution was accomplished. Therefore, for a more rapid and complete dissolution the use of larger amounts of zirconium nitrate solvent may be employed. Also application of more vigorous warming may be employed.

Approximately one cubic centimeter samples of the solution resulting from the above treatments were taken and these one cubic centimeter samples were diluted to 1 liter. However, no precipitation of the sulfates occurred even under these conditions of dilution of 1000 to 1. On the other hand in the instances of those sulfates which may be dissolved in fuming sulfuric acid, subsequent dilution of the solution causes reprecipitation.

From the foregoing, it may be observed that the use of the zirconium type of solvent of the present invention is relatively simple and merely comprises contacting the material to be dissolved with the solvent, accompanied by warming or heating as desired.

The procedure of the present invention may be utilized for various processes and in widely different fields. For example, in connection with electrical work where lead sulfate may be formed, this may be put into solution by means of the solvent of the present invention. In the pigment field for example, barium sulfate may be dissolved by the present invention and subsequently utilized. Or the present invention may be used in connection with calcium sulfate compounds in preparing plaster of Paris composition and pigments.

As indicated, the exact amounts of sulfate to be utilized and concentration thereof may be readily arrived at by one skilled in the art from a consideration of the particular character of the difiicultly soluble compound to be processed by the present invention and other related conditions. It is generally preferred to employ the smallest amount of solvent consistent with good dissolution. As a guide to quantities, for example to 50 cc. of solvent of the character described herein for each gram of material to be dissolved is usually sufficient. For very difficultly soluble materials, such as barium sulfate, larger amounts as 200 cc., or a more concentrated solvent, may be used. The exact amount is not a limitation on the present invention. Likewise other zirconium derivatives such as zirconium chloride (the Zr having a +4 valence) together with liquids such as alchohols for dissolving these zirconium compounds may be used in making up the zirconium solvent of the present invention.

It is to be understood that all matter contained in the above description and examples shall be interpreted as illustrative and not limitative of the scope of this invention, and it is intended to claim the present invention as broadly as possible in view of the prior art.

I claim:

1. In a process for dissolving a metal sulfate chosen from the group of difiicultly soluble metal sulfates consisting of the sulfates of lead, barium, strontium, and calcium, the step which comprises contacting said metal sulfate with an aqueous solution containing dissolved nitrate of tetravalent zirconium, to dissolve therein said metal sulfate.

2. In a process for dissolving a metal sulfate chosen from the group of diflicultly soluble metal sulfates consisting of the sulfates of lead, barium, strontium, and calcium, the step which comprises contacting said metal sulfate with an aqueous solution containing dissolved zirconyl nitrate, to dissolve therein said metal sulfate.

3. In a process for dissolving a metal sulfate chosen from the group of difiicultly soluble metal sulfates consisting of the sulfates of lead, barium, strontium, and calcium, the step which comprises contacting said metal sulfate with an aqueous solution approximately 2 molal with respect to zirconyl nitrate, to dissolve therein said metal sulfate.

4. The process of claim 3 in which the metal sulfate is lead sulfate.

5. The process of claim 3 in which the metal sulfate is barium sulfate.

6. The process. of claim 3 in which the metal sulfate is strontium sulfate.

7. The process of claim 3 in which the metal sulfate is calcium sulfate.

ALBERT H. AN GERMAN.

REFERENCES CITED The following references are of record in the file of this patent:

Mellor: Inorganic and Theoretical Chemistry, vol. 7, p. 161. Longmans, Green and Co., London (1927).

International Critical Tables, vol. 7, pp. 318 and 340 to 343. McGraw-I-Iill, N. Y. (1930). 

1. IN A PROCESS FOR DISSOLVING A METAL SULFATE CHOSEN FROM THE GROUP OF DIFFICULTY SOLUBLE METAL SULFATES CONSISTING OF THE SULFATES OF LEAD, BARIUM, STRONTIUM, AND CALCIUM, THE STEP WHICH COMPRISES CONTACTING SAID METAL SULFATE WITH AN AQUEOUS SOLUTION CONTAINING DISSOLVED NITRATE OF TETRAVALENT ZIRCONIUM, TO DISSOLVE THEREIN SAID METAL SULFATE. 